1. Field of the Invention
The present invention relates to a piezoelectric/electrostrictive ceramic composition.
2. Description of the Background Art
Piezoelectric/electrostrictive devices used in diesel engine injectors and the like employ an Ag/Pd-based electrode as their inner electrode in view of costs. Since the Ag/Pd-based electrode has a low melting point, it is required to reduce the firing temperature of such piezoelectric/electrostrictive ceramics. To be more specific, piezoelectric/electrostrictive ceramic compositions that are densified at a firing temperature of less than 1000° C. are desired. To this end, using a sintering agent to reduce the firing temperature has been considered. The use of a sintering agent, however, has a drawback in that the original piezoelectric/electrostrictive properties may be reduced.
Japanese Patent Application Laid-open No. 2006-188414 discloses a substance represented by the general formula: xBiMeO3-yPbZrO3-(1-x-y)PbTiO3 (where Me is Sc and/or In.) In Japanese Patent Application Laid-open No. 2008-94707, an element is selected based on the ionic radius in a perovskite structure, Bi(Al, Fe, M)O3, with Bi at the A site (M is at least any one of Cr, Mn, Co, Ni, Ga, and Sc). These composition design may promote deformation due to the tolerance factor calculated from the ionic radius, but in practical cases, satisfactory piezoelectric characteristics can not be obtained because the perovskite structure is hard to be synthesized, or availability in practical application can not be realized because of low density or because of low insulating performance due to the volatilization of the element Bi at high temperatures.
The present invention has been made in view of these conventional problems and has an object to provide a piezoelectric/electrostrictive ceramic composition with high density and excellent crystallinity, even in the case of firing under lower temperature conditions than in conventional cases; and with excellent piezoelectric/electrostrictive properties.